Method and apparatus for pulmonary artery pressure signal isolation

ABSTRACT

An implantable system senses a pulmonary artery pressure (PAP) signal using an implantable sensor placed in the pulmonary artery and isolates a plurality of signals from the PAP signal for diagnostic and/or therapeutic use. Each signal is extracted from the PAP signal using its known frequency characteristics and/or timing relationship with one or more detectable events.

TECHNICAL FIELD

This document relates generally to medical systems and particularly, butnot by way of limitation, to such a system sensing a pulmonary arterypressure (PAP) signal and isolating multiple signals for diagnosticand/or therapeutic uses from the sensed PAP signal.

BACKGROUND

Blood pressure indicates a person's cardiovascular conditions andhemodynamic performance and is sensed for various diagnostic,monitoring, and therapy-control purposes. A blood pressure signal sensedfrom a person includes signal components originated from variousphysiological and environmental sources. For example, an intravascularpressure sensor may sense a pressure signal including components ofvarious origins including, but not limited to, cardiac activities,pulmonary activities, posture, exercise, weather, altitude, atmosphericpressure, operation of a respirator, Valsalva and Mueller maneuvers,cardiopulmonary resuscitation (CPR), and various cardiovascular andother physiological conditions. Most of such components of the pressuresignal each have diagnostic and/or therapeutic value. However, eachcomponent of the pressure signal may be a signal for one diagnostic,monitoring, or therapy-control purpose but must be excluded for anotherdiagnostic, monitoring, or therapy-control purpose. In other words, eachcomponent of the pressure signal may be a signal for one purpose but anoise for another purpose.

Different components of a sensed blood pressure signal may provideinformation needed for substantially different purposes in the samemedical system performing various diagnostic, monitoring, and/ortherapy-control purposes. Therefore, there is a need for a system thatprovides for efficient processing of the sensed blood pressure signalfor each purpose.

SUMMARY

An implantable medical device processes a sensed pulmonary arterypressure (PAP) signal to isolate a plurality of signals from the PAPsignal for diagnostic, monitoring, and/or therapeutic uses. Each signalis a component of the PAP signal having one or more characteristicsallowing for its separation from other components of the PAP signal. Inone embodiment, an implantable pressure sensor is placed in thepulmonary artery to sense the PAP signal.

In one embodiment, a system for processing signals sensed by animplantable PAP sensor includes a wireless communication circuit and aPAP signal processor. The wireless communication circuit receives a PAPsignal from the implantable PAP sensor. The PAP signal processorincludes a signal isolation module that isolates a plurality of signalsfrom the PAP signal.

In one embodiment, an implantable system includes an implantable PAPsensor and an implantable medical device. The implantable sensor isconfigured for placement in the pulmonary artery to sense a PAP signal.The implantable medical device includes a PAP signal processor. The PAPsignal processor includes a signal isolation module that isolates aplurality of signals from the PAP signal.

In one embodiment, a method for processing a PAP signal is provided. APAP signal is received from an implantable PAP sensor through a wirelesscommunication link. Multiple signals are isolated from the PAP signalfor diagnostic, monitoring, and/or therapeutic uses.

This Summary is an overview of some of the teachings of the presentapplication and not intended to be an exclusive or exhaustive treatmentof the present subject matter. Further details about the present subjectmatter are found in the detailed description and appended claims. Otheraspects of the invention will be apparent to persons skilled in the artupon reading and understanding the following detailed description andviewing the drawings that form a part thereof, each of which are not tobe taken in a limiting sense. The scope of the present invention isdefined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, which are not necessarily drawn to scale, illustrategenerally, by way of example, but not by way of limitation, variousembodiments discussed in the present document.

FIG. 1 is an illustration of an embodiment of a medical system thatsenses a PAP signal using an implantable sensor and portions of anenvironment in which the medical system operates.

FIG. 2 is a graph illustrating an exemplary PAP signal.

FIG. 3 is a graph illustrating amplitude and frequency characteristicsof various components of a PAP signal.

FIG. 4 is a block diagram illustrating an embodiment of portions of acircuit of the medical system of FIG. 1.

FIG. 5 is a block diagram illustrating an embodiment of a system forprocessing the PAP signal.

FIG. 6 is a block diagram illustrating an embodiment of portions of thesystem of FIG. 5 for adjusting the PAP signal.

FIG. 7 is a block diagram illustrating an embodiment of portions of thesystem of FIG. 5 for isolating signals from the PAP signal.

FIG. 8 is a block diagram illustrating a specific embodiment of portionsof the system of FIG. 5 for isolating signals from the PAP signal.

FIG. 9 is a block diagram illustrating another specific embodiment ofportions of the system of FIG. 5 for isolating signals from the PAPsignal.

FIG. 10 is a block diagram illustrating another specific embodiment ofportions of the system of FIG. 5 for isolating signals from the PAPsignal.

FIG. 11 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device.

FIG. 12 is a block diagram illustrating an embodiment of an externalsystem communicating with the implantable medical device.

FIG. 13 is a flow chart illustrating an embodiment of a method foracquiring a plurality of signals using an implantable PAP sensor.

FIG. 14 illustrates a sensor anchoring device in accordance with oneembodiment of the present invention.

FIG. 15 is a top view of a section of the sensor anchoring device ofFIG. 14 in which a sensor is placed.

FIG. 16 is a side view of the sensor anchoring device section and sensorillustrated in FIG. 15.

FIG. 17 is a cross-sectional view of one embodiment of a sensoranchoring device positioned within a bodily cavity.

FIG. 18 is a cross-section view of another embodiment of a sensoranchoring device positioned within a bodily cavity.

FIG. 19 is a view of one embodiment of a sensor device that can beanchored in a bodily cavity in accordance with one embodiment of theinvention.

FIG. 20 is a cross-section view showing the sensor device of FIG. 19being held in place in a bodily cavity by another embodiment of a sensoranchoring device.

FIG. 21 is an axial view showing the sensor device of FIG. 19 being heldin place in a bodily cavity in accordance with one embodiment of ananchoring device.

FIG. 22 is a view of another embodiment of a sensor anchoring device.

FIGS. 23-25 are cross-section views of yet other embodiments of sensoranchoring devices positioned within bodily cavities.

FIG. 26 is a cross-sectional view of a heart showing the septal walls.

FIGS. 27A-27E are diagrams illustrating one embodiment of a method foranchoring a sensor within the septal wall of the heart.

FIG. 28 is a flow diagram illustrating delivering, positioning, andanchoring a plug-like structure into a pre-anchoring slit according toone embodiment of the present invention.

FIG. 29 is a flow diagram illustrating an exemplary algorithm forcontrollably positioning and anchoring an implantable medical device ata desired location.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the scope of the presentinvention. The following detailed description provides examples, and thescope of the present invention is defined by the appended claims andtheir legal equivalents.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one. In this document, the term“or” is used to refer to a nonexclusive or, unless otherwise indicated.Furthermore, all publications, patents, and patent documents referred toin this document are incorporated by reference herein in their entirety,as though individually incorporated by reference. In the event ofinconsistent usages between this documents and those documents soincorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

This document discusses a sensor signal processing system that isolatesvarious signals from a PAP signal. A physiological sensor senses the PAPsignal as a physiological signal indicative of PAP. The PAP signalincludes signal components having various signal and noise sources thatare physiological and environmental in nature. Such signal componentsare related to, for example, cardiac activities, respiratory activities,atmospheric pressure, weather, altitude, posture, Valsalva and Muellermaneuvers, exercise, CPR, external respiratory therapy, coughs, andsneezes. Isolation of some of these signal components from the PAPsignal allows for their therapeutic or diagnostic use. For example, arespiratory signal including isolated respiratory components of the PAPsignal provides an accurate measure of the patient's respiratory rateand respiratory cycle phase. This respiratory signal may also providefor estimation of tidal volume, minute ventilation, and otherrespiratory parameters. Additionally, the isolated respiratory componentallows proper interpretation of the PAP signal and other signalsisolated from the PAP signal. For example, to avoid the effect ofrespiration, PAP readings are taken at the end of the expiratory phaseof a respiratory cycle. A signal indicative of the expiratory phaseprovides a timing trigger for proper sampling of the PAP signal.Isolation of a low-frequency (near DC) component of the PAP signalprovides a measure of the mean PAP and relatively slow moving signalssuch as atmospheric pressure. Isolation of the cardiac component fromthe PAP signal provides greater dynamic range of the PAP signal becausethe DC offset and the respiratory component is eliminated. A cardiacsignal including isolated cardiac components of the PAP signal alsoprovides for calculation of mechanical and electromechanical cardiactiming intervals. Isolated signals indicative of changes in PAPimmediately before, during, and immediately after the performance ofintrathoracic pressure maneuvers such as Valsalva and Mueller maneuversprovide for assessment of cardiac performance, including detection ofpotential heart failure.

The sensor signal processing system isolates desired signals from thePAP signal by using distinctive characteristics of each signal to beisolated. The isolated signals serve multiple diagnostic, monitoring,and/or therapy-control purposes. In one embodiment, the physiologicalsensor that senses the PAP signal is an implantable PAP sensor thatsenses the PAP. In other embodiments, the physiological sensor thatsenses the PAP signal is an implantable or external sensor that sensesthe PAP or a signal representative of the PAP. In one embodiment, animplantable medical device receives the PAP signal from thephysiological sensor and includes the sensor signal processing system toisolate a plurality of signals from the PAP signal. In anotherembodiment, an external device receives the PAP signal from thephysiological sensor and includes the sensor signal processing system toisolate a plurality of signals from the PAP signal.

FIG. 1 is an illustration of one embodiment of a medical system 100 andportions of an environment in which system 100 operates. System 100includes an implantable PAP sensor 110, an implantable medical device112, an external system 114, a communication link 111 between PAP sensor110 and implantable medical device 112, and a communication link 113between implantable medical device 112 and external system 114.

As illustrated in FIG. 1, implantable PAP sensor 110 and implantablemedical device 112 are implanted in a body 102 that has a pulmonaryartery 103 connected to a heart 101. The right ventricle of heart 101pumps blood through pulmonary artery 103 to the lungs of body 102 to getoxygenated. Implantable PAP sensor 110 is a pressure sensor configuredfor being mounted on a portion of the interior wall of pulmonary artery103 to sense a PAP signal. The sensed PAP signal is transmitted toimplantable medical device 112 through communication link 111. In oneembodiment, communication link 111 includes a wired communication linkformed by a lead connected between implantable PAP sensor 110 andimplantable medical device 112. In another embodiment, communicationlink 111 includes an intra-body wireless telemetry link. Implantablemedical device 112 includes a sensor signal processing system thatreceives and processes the PAP signal sensed by implantable PAP sensor110. The sensor signal processing system includes a PAP signal processor120 that isolates a plurality of signals of substantially differenttypes from the PAP signal for diagnostic, monitoring, and/ortherapy-control uses. In various embodiments, implantable medical device112 is an implantable CRM device including one or more of aphysiological monitor, a pacemaker, a cardioverter/defibrillator, acardiac resynchronization therapy (CRT) device, a cardiac remodelingcontrol therapy (RCT) device, a neural stimulator, a drug deliverydevice or a drug delivery controller, and a biological therapy device.In various embodiments in which one or more signals in addition to thePAP signal are sensed, and/or one or more therapies are delivered, alead system 108 provides for electrical and/or other connections betweenbody 102 and implantable medical device 112. In various embodiments,lead system 108 includes leads for sensing physiological signals anddelivering pacing pulses, cardioversion/defibrillation shocks, neuralstimulation pulses, pharmaceutical agents, biological agents, and/orother types of energy or substance for treating cardiac disorders. Inone embodiment, as illustrated in FIG. 1, lead system 108 provides forsuch electrical and/or other connections between heart 101 andimplantable medical device 112.

External system 114 allows a user such as a physician or other caregiverto control the operation of implantable medical device 112 and obtaininformation acquired by implantable medical device 112. In oneembodiment, external system 114 includes a programmer communicating withimplantable medical device 112 bi-directionally via communication link113, which is a telemetry link. In another embodiment, external system114 is a patient management system including an external devicecommunicating with a remote device through a telecommunication network.The external device is within the vicinity of implantable medical device112 and communicates with implantable medical device 112bi-directionally via communication link 113. The remote device allowsthe user to monitor and treat a patient from a distant location. Thepatient monitoring system is further discussed below, with reference toFIG. 12.

Communication link 113 provides for data transmission from implantablemedical device 112 to external system 114. This includes, for example,transmitting real-time physiological data acquired by implantablemedical device 112, extracting physiological data acquired by and storedin implantable medical device 112, extracting therapy history datastored in implantable medical device 112, and extracting data indicatingan operational status of implantable medical device 112 (e.g., batterystatus and lead impedance). The real-time and stored physiological dataacquired by implantable medical device 112 include data representativeof the PAP signal sensed by implantable PAP sensor 110. Telemetry link113 also provides for data transmission from external system 114 toimplantable medical device 112. This includes, for example, programmingimplantable medical device 112 to acquire physiological data,programming implantable medical device 112 to perform at least oneself-diagnostic test (such as for a device operational status), andprogramming implantable medical device 112 to deliver at least onetherapy.

In various embodiments, PAP signal processor 120, including its specificembodiments as discussed below, is implemented by hardware, software, ora combination of hardware and software. In various embodiments, PAPsignal processor 120 includes elements such as those referred to asmodules below that are each an application-specific circuit constructedto perform one or more particular functions or a general-purpose circuitprogrammed to perform such function(s). Such a general-purpose circuitincludes, but is not limited to, a microprocessor or a portion thereof,a microcontroller or portions thereof, and a programmable logic circuitor a portion thereof.

It is to be understood that while system 100 is specifically discussedin this document as an illustrative example, the present subject matteris not limited to embodiments using an implantable PAP sensor and/or animplantable medical device that includes the sensor signal processingsystem. For example, the PAP signal can be sensed by a non-implantablesensor, and the sensor signal processing system can be implemented in anon-implantable device.

FIG. 2 is a graph illustrating an exemplary PAP signal 204. PAP signal204 is primarily a cardiac signal including a respiratory signalcomponent 205. PAP signal 204 represents the PAP, which changes withcardiac cycles. Respiratory signal component 205 indicates respiratorycycles. PAP signal 204 also includes signal components from variousother sources such as atmospheric pressure, posture, weather, altitude,Valsalva maneuvers, and Mueller maneuvers.

FIG. 3 is a graph illustrating amplitude and frequency characteristicsof various components of a PAP signal. Such characteristics provide forbases upon which various signals can be isolated from the PAP signal fordiagnostic, monitoring, and/or therapy-control uses.

FIG. 4 is a block diagram illustrating an embodiment of portions of acircuit of system 100. Implantable PAP sensor 110 is an integratedcircuit sensor that includes a sensor telemetry circuit 422, which is awireless communication circuit, in addition to its pressure-sensingelement. Implantable medical device 112 includes an implant telemetrycircuit 424, in addition to PAP signal processor 120 and, if applicable,other sensing and/or therapeutic elements. In one embodiment, implanttelemetry circuit 424 includes a sub-circuit supporting communicationlink 111 and another sub-circuit supporting communication link 113.External system 114 includes an external telemetry circuit 426, inaddition to programming and other patient management elements.

In one embodiment, communication link 111 is an ultrasonic telemetrylink. Sensor telemetry circuit 422 includes an ultrasonic telemetrytransmitter that transmits the PAP signal by modulating an ultrasonicsignal using the PAP signal and transmitting the modulated ultrasonicsignal. Implant telemetry circuit 424 includes an ultrasonic telemetryreceiver that receives the PAP signal by demodulating the modulatedultrasonic carrier signal. An example of an intra-body ultrasonictelemetry system is discussed in U.S. patent application Ser. No.10/888,956, entitled “METHOD AND APPARATUS OF ACOUSTIC COMMUNICATION FORIMPLANTABLE MEDICAL DEVICE,” filed on Jul. 9, 2004, assigned to CardiacPacemakers, Inc., which is incorporated herein by reference in itsentirety. In another embodiment, communication link 111 is a far-fieldradio-frequency (RF) telemetry link. Sensor telemetry circuit 422includes a far-field RF telemetry transmitter that transmits the PAPsignal by modulating an electromagnetic signal using the PAP signal andtransmitting the modulated electromagnetic signal. Implant telemetrycircuit 424 includes a far-field RF telemetry receiver that receives thePAP signal by demodulating the modulated electromagnetic carrier signal.In another embodiment, communication link 111 is an inductive telemetrylink. Sensor telemetry circuit 422 includes an inductive telemetrytransmitter that transmits the PAP signal by modulating a magnetic fieldusing the PAP signal. Implant telemetry circuit 424 includes aninductive telemetry receiver that receives the PAP signal bydemodulating the modulated magnetic field. In one embodiment,communication link 111 is a bidirectional telemetry link that allows fortransmission of the PAP signal from implantable PAP sensor 110 toimplantable medical device 112 as well as transmission of signals suchas command signals from implantable medical device 112 to implantablePAP sensor 110 for controlling the operation of implantable PAP sensor110. Sensor telemetry circuit 422 and implant telemetry circuit 424 eachinclude an ultrasonic, far-field RF, or inductive telemetry transceiverto support communication link 111.

In various embodiments, communication link 113 is a bidirectionalultrasonic, far-field RF, or inductive telemetry link. Implant telemetrycircuit 424 and external telemetry circuit 426 each include anultrasonic, far-field RF, or inductive telemetry transceiver to supportcommunication link 113.

Communication links 111 and 113 are illustrated in FIG. 3 and discussedabove for illustrative but not restrictive purposes. Other communicatingschemes are useable to transmit the sense PAP signal from implantablePAP sensor 110 to implantable medical device 112, from implantablemedical device 112 to external system 114, or from implantable PAPsensor 110 to external system 114. In one embodiment, an insulated wirecan provide an electrical connection between implantable PAP sensor 110and implantable medical device 112 for transmitting the PAP signal. Inanother embodiment, implantable PAP sensor 110 communicates directlywith external system 114 using an ultrasonic, far-field RF, or inductivetelemetry link through which the PAP signal is transmitted.

FIG. 5 is a block diagram illustrating an embodiment of a system forprocessing the PAP signal including a PAP signal processor 520, one ormore environmental sensors 532, and one or more physiological sensors534. PAP signal processor 520 is a specific embodiment of PAP signalprocessor 120. Environmental sensor(s) 532 and physiological sensor(s)534 are each a sensor contained within implantable medical device 112 orcoupled to implantable medical device 112 via an electrical or telemetryconnection.

PAP signal processor 520 includes a signal adjustment module 528 and asignal isolation module 530. Signal adjustment module 528 adjusts thePAP signal by removing one or more unwanted signal components inpreparation for isolation of a plurality of wanted signal components bysignal isolation module 530. Environmental sensor(s) 532 sense one ormore environmental signals related to the one or more unwanted signalcomponents that have one or more environmental origins. Physiologicalsensor(s) 534 sense one or more physiological signals related to the oneor more unwanted signal components that have one or more physiologicalorigins.

In one embodiment, PAP signal processor 520 digitizes the PAP signalreceived from implant telemetry circuit 424 before further processing. Apreamplifier and filter circuit receives the PAP signal and amplifiesand filters the PAP signal. In various embodiments, the preamplifier andfilter circuit is part of PAP signal processor 520, part of implanttelemetry circuit 424, or distributed in both PAP signal processor 520and implant telemetry circuit 424. The amplified and filtered PAP signalis then digitized using an analog-to-digital converter (ADC) beforebeing adjusted by signal adjustment module 528. In one embodiment, thepreamplifier and filter circuit has a gain in a range of approximately 1to 10 and a pass-band with a low cutoff frequency in a range ofapproximately 0.000001 Hz to 0.1 Hz and a high cutoff frequency in arange of approximately 3 Hz to 30 Hz. The ADC has a sample rate in arange of approximately 5 Hz to 50 Hz. In a specific embodiment, thepreamplifier and filter circuit has a gain of approximately 1 and apass-band with a low cutoff frequency of approximately 0.01 Hz and ahigh cutoff frequency of approximately 5 Hz. The ADC has a sample rateof approximately 20 Hz.

FIG. 6 is a block diagram illustrating an embodiment of a system foradjusting the sensed PAP signal including a signal adjustment module628, an external pressure calibrator 642, and a posture sensor 646.Signal adjustment module 628 is a specific embodiment of signaladjustment module 528. External pressure calibrator 642 is one ofenvironmental sensor(s) 532. Posture sensor 646 is one of physiologicalsensor(s) 534.

Signal adjustment module 628 includes an atmospheric pressure adjustmentmodule 636, a posture adjustment module 638, and a pruning module 640.Atmospheric pressure adjustment module 636 adjusts the PAP signal usingan atmospheric pressure sensed by external pressure calibrator 642,which includes a barometer 644. In one embodiment, external pressurecalibrator 642 is a portable device to be placed near implantablemedical device 112 and communicates with atmospheric pressure adjustmentmodule 636 via telemetry. Posture adjustment module 638 adjusts the PAPsignal for effects related to posture as sensed by posture sensor 646.Pruning module 640 algorithmically prunes predetermined type outliercomponents from the sensed PAP signal.

In various embodiments, signal adjustment module 628 includes one ormore of atmospheric pressure adjustment module 636, posture adjustmentmodule 638, pruning module 640, and other adjustment modules foradjusting the PAP signal. In one embodiment, implantable medical device112 includes a respiratory sensor such as an impedance sensor sensing animpedance signal indicative of respiratory cycles, and signal adjustmentmodule 628 includes a respiratory adjustment module to remove the effectof respiration in the PAP signal.

FIG. 7 is a block diagram illustrating an embodiment of a signalisolation module 730, which is a specific embodiment of signal isolationmodule 530. As illustrated in FIG. 7, signal isolation module 730includes a cardiac signal isolation module 750 that isolates one or morecardiac signals from the sensed PAP signal, a respiratory signalisolation module 751 that isolates one or more respiratory signals fromthe PAP signal, an atmospheric pressure signal isolation module 752 thatisolates an atmospheric pressure signal from the PAP signal, a posturesignal isolation module 753 that isolates a posture signal from the PAPsignal, a weather signal isolation module 754 that isolates a weathersignal from the PAP signal, an altitude signal isolation module 755 thatisolates an altitude signal from the PAP signal, a Valsalva signalisolation module 756 that isolates a Valsalva signal from the PAPsignal, and a Mueller signal isolation module 757 that isolates aMueller signal from the PAP signal. In various other embodiments, signalisolation module 730 includes any one or more of cardiac signalisolation module 750, respiratory signal isolation module 751,atmospheric pressure signal isolation module 752, posture signalisolation module 753, weather signal isolation module 754, altitudesignal isolation module 755, Valsalva signal isolation module 756, andMueller signal isolation module 757.

The cardiac, respiratory, atmospheric pressure, posture, weather,altitude, Valsalva, and Mueller signals are each isolated for directand/or indirect diagnostic monitoring, and/or therapy-control uses. Forexample, the one or more cardiac signals are indicative of cardiacperformance parameters such as stroke volume as well as heart failure(HF) decompensation. The one or more respiratory signals are indicativeof pulmonary performance parameters such as tidal volume as well asperiodic breathing. Parameters derived from such cardiac and respiratorysignals are useable for monitoring a patient's cardiopulmonary health,including state of HF, and/or for controlling one or more therapies forimproving hemodynamic performances. The posture signal is used toindirectly detect posture changes or to remove effects of posture insensed physiological signals such as various blood pressure signals. Theatmospheric, weather, and altitude signals are used to indirectly detectatmospheric, weather, and altitude changes and to remove effects ofenvironmental factors in sensed physiological signals such as variousblood pressure signals. The Valsalva signal includes components of thePAP signal that indicates changes in PAP immediately before, during, andimmediately after a Valsalva maneuver. The Mueller signal includescomponents of the PAP signal that indicates changes in PAP immediatelybefore, during, and immediately after a Mueller maneuver. The Valsalvaand Muller signals each provide for assessment of cardiac performance,including detection or prediction of HF. An example of assessing cardiacperformance using Valsalva maneuver is discussed in U.S. patentapplication Ser. No. 10/782,642, entitled “SYSTEM AND METHOD FORASSESSING CARDIAC PERFORMANCE THROUGH TRANSCARDIAC IMPEDANCEMONITORING,” filed on Feb. 19, 2004, assigned to Cardiac Pacemakers,Inc., which is incorporated by reference herein in its entirety. Invarious embodiments, the content and characteristics of the cardiac,respiratory, atmospheric pressure, posture, weather, altitude, Valsalva,and Mueller signals to be isolated from the PAP signal are eachdetermined based on the intended use of that signal in diagnosis,monitoring, and/or therapy-control.

Signal isolation modules 750-757 each isolate one or more signals fromthe PAP signal by using amplitude and frequencies characteristics of thevarious components of the PAP signal, such as these illustrated in FIG.3, as well as timing relationships between those one or more signals andother detectable signals or events. Isolation of several cardiac andrespiratory signals is discussed with reference to FIGS. 8-10 asspecific examples, but not limitations, to illustrate how signalisolation modules 750-757 isolate the one or more signals from the PAPsignal. Upon reading and understanding this document, those skilled inthe art will understand how to isolate signals such as cardiac,respiratory, atmospheric pressure, posture, weather, altitude, Valsalva,and Mueller signals, for specifically intended uses in diagnosis,monitoring, and/or therapy-control by using techniques and structuralapproaches identical or similar to those illustrated in FIGS. 8-10.

FIG. 8 is a block diagram illustrating an embodiment of a signalisolation module 830, which is another specific embodiment of signalisolation module 530. Signal isolation module 830 includes a cardiacsignal isolation module 850 and a respiratory signal isolation module851.

Cardiac signal isolation module 850 includes a filter 860. In oneembodiment, filter 860 includes a band-pass filter having apredetermined pass band. In a specific embodiment, the band-pass filteris used to isolate a cardiac signal including the dicrotic notch. Thepass band has a low cutoff frequency of approximately 0.3 Hz and a highcutoff frequency of approximately 20 Hz. In another specific embodiment,the band-pass filter is used to isolate a cardiac signal including heartfailure (HF) decompensation. The pass band has a low cutoff frequency ofapproximately 0.0000001 Hz and a high cutoff frequency of approximately0.0001 Hz.

Respiratory signal isolation module 851 includes a filter 861. In oneembodiment, filter 861 includes a band-pass filter having apredetermined pass band. In a specific embodiment, the band-pass filteris used to isolate a respiratory signal indicative of tidal volume byremoving the weather and altitude components of the PAP signal. The passband has a low cutoff frequency of approximately 0.08 Hz and a highcutoff frequency of approximately 5 Hz. In another specific embodiment,the band-pass filter is used to isolate a respiratory signal indicativeof periodic breathing. The pass band has a low cutoff frequency ofapproximately 0.01 Hz and a high cutoff frequency of approximately 0.05Hz.

FIG. 9 is a block diagram illustrating an embodiment of a signalisolation module 930 and a heart rate detector 962. Signal isolationmodule 930 is another specific embodiment of signal isolation module 530and includes a cardiac signal isolation module 950 and a respiratorysignal isolation module 951. While FIG. 3 shows that the spectrums ofcardiac and respiratory signals overlap at around 1 Hz, the spectrumsreflect the frequency characteristics over a range of heart rates, andit is observed that the spectrums of cardiac and respiratory signals donot substantially overlap at each specific heart rate. Thus, heart ratedetector 962 detects a heart rate for use as a control signal forseparating the cardiac and respiratory signals in the PAP signal usingtheir frequency characteristics.

Cardiac signal isolation module 950 includes an adaptive filter 960. Inone embodiment, adaptive filter 960 includes a band-pass filter having adynamically adjustable pass band. In a specific embodiment, such anadaptive band-pass filter is used to isolate a cardiac signal indicativestroke volume. The pass-band includes a low cutoff frequency that isdynamically adjustable in a range of approximately 0.5 Hz to 1.0 Hz, anda high cutoff frequency that is approximately 20 Hz. In anotherembodiment, adaptive filter 960 includes a notch filter having adynamically adjustable rejection band. In a specific embodiment,referring to FIG. 3, such an adaptive notch filter is used to isolate acardiac signal indicative HF decompensation and stroke volume. Therejection band includes a low cutoff frequency that is approximately0.0001 Hz and a high cutoff frequency that is dynamically adjustable inrange of approximately 0.5 Hz to 1.0 Hz.

Respiratory signal isolation module 951 includes an adaptive filter 961.In one embodiment, adaptive filter 961 includes a band-pass filterhaving a dynamically adjustable pass band. In a specific embodiment,such an adaptive band-pass filter is used to isolate a respiratorysignal indicative of tidal volume. The pass band includes a low cutofffrequency that is dynamically adjustable in a range of approximately0.01 Hz, and the high cutoff frequency that is approximately 0.5 Hz to1.0 Hz.

The pass bands of adaptive filters 960 and 961 are each dynamicallyadjustable using a physiological signal or parameter. In the embodimentillustrated in FIG. 9, heart rate detector 962 detects the heart rate asthe physiological signal or parameter. That is, the pass bands ofadaptive filters 960 and 961 are each a function of the heart rate andeach adjusted in response to a substantial change in the detected heartrate.

FIG. 10 is a block diagram illustrating an embodiment of a signalisolation module 1030 and a respiratory sensor 1066. Signal isolationmodule 1030 is another specific embodiment of signal isolation module530 and includes a cardiac signal isolation module 1050. Knowing theeffects of respiration on the PAP signal, cardiac signal isolationmodule 1050 isolates a cardiac signal from the PAP by excluding theeffects of the respiration. Respiratory sensor 1066 senses a respiratorysignal indicative of respiratory cycles and pattern based on which theeffects of respiration can be excluded. In general, effects of cyclicphysiological signals such as those associated with cardiac andrespiratory cycles can be substantially excluded or attenuated bytriggered sampling.

Cardiac signal isolation module 1050 includes a triggered sampler 1064that samples the PAP signal at a predetermined type event in eachrespiratory cycle. For example, the PAP signal is to be evaluated at theend of expiration to avoid the effects of respiration. By sampling thePAP signal at each end of expiration as indicated in the respiratorysignal sensed by respiratory sensor 1066, triggered sampler 1064isolates a cardiac signal from the PAP signal. In one embodiment,respiratory sensor 1066 is a minute ventilation sensor that is animplantable impedance sensor that senses an impedance indicative of lungvolume.

FIG. 11 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device 1112, which is a specificembodiment of implantable medical device 112. Implantable medical device1112 includes implant telemetry circuit 424, PAP signal processor 120, atherapy delivery device 1170, and a controller 1172.

Therapy delivery device 1170 delivers one or more therapies such aspacing therapy, cardioversion/defibrillation therapy, CRT, RCT, neuralstimulation therapy, drug therapy, and biological therapy. Controller1172 controls the delivery of the one or more therapies using at leastone signal of the plurality of signals provided by PAP signal processorby isolation from the PAP signal received from implantable PAP sensor110 via communication link 111. In one embodiment, therapy deliverydevice 1170 includes a pacing circuit 1174 to deliver pacing pulses, andcontroller 1172 includes a CRT control module 1176 to control thedelivery of the pacing pulses by executing a CRT pacing algorithm.

FIG. 12 is a block diagram illustrating an embodiment of an externalsystem 1214, which is a specific embodiment of external system 114. Asillustrated in FIG. 12, external system 1214 is a patient managementsystem including an external device 1280, a telecommunication network1282, and a remote device 1284. External device 1280 is placed withinthe vicinity of the implantable medical device 112 and includes externaltelemetry system 426 to communicate with the implantable medical device112 via telemetry link 113. Remote device 1284 is in one or more remotelocations and communicates with external device 1280 through network1282, thus allowing a user to monitor and treat a patient from a distantlocation and/or allowing access to various treatment resources from theone or more remote locations.

FIG. 13 is a flow chart illustrating an embodiment of a method foracquiring a plurality of signals using an implantable PAP sensor. In oneembodiment, the method is performed by system 100.

A PAP signal is received from an implantable PAP sensor through atelemetry link at 1300. In one embodiment, the implantable PAP sensor isplaced within the pulmonary artery to sense a PAP signal. In oneembodiment, an ultrasonic signal is received through an ultrasonictelemetry link, and the PAP signal is received by demodulating theultrasonic signal. In another embodiment, an electromagnetic signal isreceived through a far-field RF telemetry link, and the PAP signal isreceived by demodulating the electromagnetic signal. In anotherembodiment, a magnetic signal is received through an inductive telemetrylink, and the PAP signal is received by demodulating the magneticsignal.

The PAP signal is adjusted at 1310. Examples of adjustment of the PAPsignal include calibration for environmental factors, correction foreffects of physiological activities or conditions, and pruning of knowntype outlier signal components. In one embodiment, the PAP signal isadjusted using an atmospheric pressure. In a further embodiment, the PAPsignal is adjusted using a signal indicative of posture.

A plurality of signals is isolated from the PAP signal at 1320. Theplurality of signals include, for example, one or more cardiac signals,one or more respiratory signals, an atmospheric pressure signal, aposture signal, a weather signal, an altitude signal, a Valsalva signal,and/or a Mueller signal. Such signals are each isolated from the PAPsignal using its unique frequency, timing, and/or amplitudecharacteristics. In various embodiments, one or more signals areisolated from the PAP signal using a filter, based on their frequencycharacteristics illustrated in FIG. 3. In one embodiment, signals withfrequency characteristics being functions of a detected physiologicalsignal or parameter are isolated by filtering the PAP signal using oneor more adaptive filters each having one or more characteristicfrequencies that are dynamically adjustable using that physiologicalsignal or parameter. In a specific embodiment, a cardiac signal and arespiratory signal are each isolated from the PAP signal by using suchan adaptive filter with at least one cutoff frequency being dynamicallyadjustable in response to changes in a detected heart rate. In oneembodiment, signals with timing characteristics related to a detectedphysiological signal or parameter are isolated by controlling the timingof the sampling of the PAP signal using that physiological signal orparameter. In a specific embodiment, one or more cardiac signals areisolated by sampling the PAP signal at a predetermined type event ineach respiratory cycle detected from a sensed signal indicative ofrespiratory cycles.

One or more therapies are controlled using one or more signals isolatedfrom the PAP signal at 1330. In one embodiment, the one or moretherapies are delivered using an implantable medical device. In aspecific embodiment, the implantable medical device performs steps1300-1330. In another specific embodiment, the implantable medicaldevice and an external system communicating with the implantable medicaldevice perform steps 1300-1330. In another embodiment, an externalsystem communicating with the implantable PAP sensor performs” steps1300-1330. Examples of the one or more therapies include pacing therapy,cardioversion/defibrillation therapy, CRT, RCT, neural stimulationtherapy, drug therapy, and biological therapy. In one specificembodiment, pacing pulses are delivered according to a CRT algorithmusing one or more signals isolated from the PAP signal.

FIGS. 14-29 illustrate exemplary embodiments of apparatus and method fordelivering, positioning, and anchoring an implantable PAP sensor. Theseexamples are also discussed in U.S. patent application Ser. No.11/216,738, entitled “DEVICES AND METHODS FOR POSITIONING AND ANCHORINGIMPLANTABLE SENSOR DEVICES,” filed on Aug. 31, 2005, assigned to CardiacPacemakers, Inc., which is incorporated herein by reference in itsentirety.

FIG. 14 shows one embodiment of a physiologic sensor anchoring system1400. In accordance with the illustrated embodiment, anchoring system1400 comprises a stent-like structure 1402 carrying a physiologicparameter sensor 1404 (e.g., pressure sensor). The stent-like structuregenerally has a tubular shape like a stent, and is adapted to carry thesensor 1404 into a bodily vessel. In this particular embodiment, thephysiologic parameter sensor 1404 is embedded in a mesh structure of thestent-like structure 1402, as is illustrated in a close-up view in FIG.15.

The sensor 1404 may be secured to and carried by the stent-likestructure 1402 in any number of ways. For example, as illustrated inFIG. 16, sensor 1404 can rest in a recessed diaphragm 1406 positioned inthe stent 1402. In alternative embodiments, sensor 1404 can be securedwithin the stent using other securing mechanisms, such as adhesives,welding techniques, or the like. In addition, sensor 1404 is configuredto communicate with implantable medical devices (IMDs), such as cardiacrhythm management device, and/or devices outside of a patient body.Examples of the sensors, sensor configurations, and communicationsystems and methods discussed in this document are discussed in moredetail in U.S. patent application Ser. No. 10/943,626 entitled “SYSTEMSAND METHODS FOR DERIVING RELATIVE PHYSIOLOGIC PARAMETERS,” U.S. patentapplication Ser. No. 10/943,269 entitled “SYSTEMS AND METHODS FORDERIVING RELATIVE PHYSIOLOGIC PARAMETERS USING AN EXTERNAL COMPUTINGDEVICE,” U.S. patent application Ser. No. 10/943,627 entitled “SYSTEMSAND METHODS FOR DERIVING RELATIVE PHYSIOLOGIC PARAMETERS USING A BACKENDCOMPUTING SYSTEM,” and U.S. patent application Ser. No. 10/943,271entitled “SYSTEMS AND METHODS FOR DERIVING RELATIVE PHYSIOLOGICPARAMETERS USING AN IMPLANTED SENSOR DEVICE,” and filed by Abhi Chavanet al. (Attorney Docket No. 306663), all assigned to Cardiac Pacemakers,Inc., which are incorporated herein by reference in their entirety andare collectively referred to as the “Physiologic Parameter SensingSystems and Methods Patents” in this document.

In other embodiments, anchoring system 1400 may be used for theplacement of IMDs with therapeutic functions such as actuating devices.For example, common actuators include, but are not limited to, anultrasound sensor and a drug delivery pod. In some embodiments,anchoring system 1400 may be used to place a plurality of sensors,actuators, or a combination of sensors and actuators. Placement ofmultiple sensors and/or actuating devices throughout the body can allowfor a more comprehensive therapeutic and diagnostic system, but multiplesensors and/or actuating devices are not required.

By using a stent-like anchoring structure, a sensor or any IMD can beanchored and secured in any part of the vascular system. In oneparticular embodiment, the stent-structure can be a balloon expandablestent, which can be placed in the vascular system using knowncatheterization techniques. For example, in one embodiment, thestent-structure can be positioned and secured in the pulmonary arteryusing techniques similar to a Swan Ganz technique, or other similarcatheterization techniques. In this particular embodiment, when thestent-like anchoring mechanism 1402 is expanded, sensor 1404 will beplace next to, or in close proximity to the vessel wall, allowing thesensor to obtain measurements from next to the vessel wall, which can bebeneficial in many situations. As one skilled in the art willappreciate, for anchoring sensors in large cavities and/or arteries,stent-like anchoring mechanism 1402 may be larger than a traditionalstent device. However, the device configuration can be similar.

A balloon deployable stent can be made of stainless steel, cobaltchromium, nitinol, and the like. The material composition of the stentmay be determined based on a variety of factors. For example, a stentplaced in an artery in a patient's neck typically has a shape-memorybecause the stent may be deformed by exogenous pressures. In contrast, astent positioned in the heart will have the protection of the patient'srib cage to help protect the stent from outside forces. Thus, it is notas important for a stent that is positioned in the heart to be made of amemory retaining material.

The stent is typically located on the outside of the balloon. As such,while inflating the balloon the stent expands. In many instances, it isdesirable to activate and test the sensor during the placement, orpositioning, phase. However, one potential problem with the balloonexpandable stent approach is that while the balloon is inflated, theblood flow through the artery may be reduced or completely blocked.Hence, the sensor may not be able to provide an accurate measurementduring placement. In addition, if the procedure is complicated,positioning of the sensor or actuator may take more time than thepatient can safely be with reduced blood flow, or without blood flowentirely, in that area.

The balloon composed of a semi-permeable or permeable membrane. Forexample, the balloon may have holes, or paths, which allow the blood toflow. Another possible solution is for the balloon to be in a shape,such as a cloverleaf shape, that provides pockets through which bloodcan continue to flow while the balloon is inflated. A cloverleaf shapewill not completely block the artery, as blood will be able to flowbetween the pedals of the clover shaped balloon. These techniques allowthe sensor to be activated and tested during the positioning of thedevice, some benefits of which are discussed below.

In some embodiments, by using a stent-like anchoring structure, aphysician can perform two functions at once; i.e., use a stent to expandand support a vessel while placing a physiologic parameter sensor in adesired location. Also, using a stent-like structure can have additionalbenefits, such as, for example: (1) the stent structure, if coated withone or more drugs to minimize inflammation, can help inhibit the longterm inflammation of artery or vessel tissue, which can occur when otheranchoring techniques are used; (2) when using a self expanding stent,the sensor can be tested prior to anchoring, and if there are problemswith the sensor, it can be retracted prior to deploying the stent-likeanchoring device; (3) the controlled deployment of the stent-structurecan prevent incorrect anchoring within the artery or vessel, which canlead to serious thrombolytic effects; and (4) the stent-like structuremight assist in evoking a limited tissue growth response over the sensoranchor, thus holding the sensor in place (a further embodiment of thisconcept is discussed in more detail below.

In accordance with these embodiments of the invention, the specific typeof stent and its anchoring location is not limited. For example, thestent-like structure can be made of titanium, stainless steel, nitinol,or some other suitable bio-compatible material, and the stent-likestructure design is not limited to any particular configuration.Further, as discussed above, the stent-like structure can be place inany part of the vascular system, including but not limited to, anyvenous or aortic blood vessel, the pulmonary artery, blood vesselsdistal from the heart, or any cardiac separating or enclosing wall(e.g., the atrial septum). In addition, as discussed above, the sensorcan be configured to measure any physiologic parameter value, includingany physical, chemical or biologic property or parameter. Finally, inone embodiment, the stent-like structure and/or sensor can be coatedwith drugs or other materials, which can reduce thrombolytic orinflammatory effects, promote fibrosis, or the like.

FIG. 17 illustrates another embodiment of a physiologic parameter sensorand anchoring system 1500. In the embodiment illustrated in FIG. 17,system 1500 comprises an anchoring device 1502, a physiologic parametersensor 1504, and one or more leads 1506 attached to sensor 1504. In thisparticular embodiment, anchoring device 1502 comprises a stent-likeanchoring device, similar to the stent-like structure discussed above.In FIG. 17, anchoring device 1502 is shown expanded and anchored in ablood vessel 1508. Again, as discussed above, vessel 1508 can be anyblood vessel within the body. In addition, anchoring device 1502 is notlimited to stent-like structure. Other anchoring devices, such as thedevices discussed below, also can be used. Further, embodiments of thepresent invention are not limited to obtaining physiologic measurementswithin blood vessels.

In this particular embodiment, sensor 1504 is attached or connected tolead 1506, and lead 1506 is further attached to anchoring device 1502.Thus, the purpose of anchoring device 1502 is to hold the sensor 1504and lead 1506 configuration in a particular location in a vessel orother bodily cavity. As discussed in more detail in the PhysiologicParameter Sensing Systems and Methods Patents, lead 1506 can facilitatecommunication between sensor 1504 and an IMD, such as a cardiac rhythmmanagement IMD. Lead 1506 can carry sensor measurements from sensor 1504to the IMO, as well as therapy and/or other information from the IMD tothe sensor 1504. Further, lead 1506 can be any suitable bio-compatiblelead (e.g., silicone, polyurethane, etc.) currently known or laterdeveloped.

FIG. 18 shows yet another embodiment of a physiologic parameter sensorand anchoring system 1600. In the embodiment illustrated in FIG. 18,system 1600 also comprises an anchoring device 1602, a physiologicparameter sensor 1604, and one or more leads 1606 attached to sensor1604 and/or anchoring device 1602. According to various embodiments, theleads 1606 may be a conductor, such as a braided cable. Examples ofmaterial from which the tether may be formed include, but are notlimited to, MP35N, stainless steel, and other standard lead conductors.According to some embodiments, the diameters of the leads 1606 typicallyrange from 0.006 to 0.009 inches. In other embodiments, the diameters ofthe leads have a much larger range.

As with the embodiment illustrated in FIG. 17, anchoring device 1602comprises a stent-like anchoring device, but other anchoring devices canbe used. In FIG. 18, anchoring device 1602 is shown expanded andanchored in a blood vessel 1608. Again, as discussed above, vessel 1608can be any blood vessel within the body, or any other bodily cavity, andembodiments of the present invention are not limited to obtainingphysiologic measurements within blood vessels.

In this particular embodiment, sensor 1604 is connected to anchoringdevice 1602. Lead 1606 is attached to sensor 1604, and can be configuredto communicate information to/from an IMD (e.g., a cardiac rhythmmanagement IMD), as discussed in more detail in the PhysiologicParameter Sensing Systems and Methods Patents referenced above. Forexample, lead 1606 can carry sensor measurements from sensor 1604 to theIMD, as well as therapy and/or other information from the IMD to thesensor. Thus, one function of anchoring device 1602 is to hold thesensor 1604 in a particular location in a vessel or other bodily cavity,and one function of lead 1604 is to facilitate communication with theIMD.

FIG. 19 illustrates one embodiment of a sensor device 1700 that can bepositioned and anchored within a bodily cavity, such as a blood vessel,or the like. In the embodiment illustrated in FIG. 19, sensor device1700 comprises a sensing mechanism (e.g., pressure sensor, circuitry,etc.) 1702 and one or more fins or extensions 1704 that can facilitatethe anchoring of sensor device 1700 in a bodily vessel. In addition tofins 1704, the sensor 1700 may have a Dacron skirt (not shown) thatpromotes fibrous ingrowth/overgrowth. In one embodiment, the skirt issimilar to those used on myocardial leads. By the time the stentbio-absorbs, such a skirt will have securely grown to the wall of thevessel. The Dacron skirt can be positioned on the bottom of the sensor1700, but can also extend beyond the dimensions of the sensor 1700.

With regard to embodiments that include outwardly extending fins 1704,the stent-like structure 1706 may include sleeves (not shown) formed ona wall of the stent-like structure 1706 and configured for receiving andholding the fins 1704. Thus, the sensor device 1700 can be attached tothe stent-like structure 1706 by sliding the fins 1704 intocorresponding sleeves of the stent-like structure 1706. The sleeves maybe configured to allow for tissue fibrosis, thereby enabling gradualtissue growth over the fins 1704 to secure the sensor device 1700 to awall of the bodily vessel 1708.

According to some embodiments, the extension beyond the dimensions ofthe sensor 1700 is similar to the configuration in epicardial (EPI)leads. As shown in FIG. 20, sensor device 1700 can be positioned withinthe bodily vessel (e.g., blood vessel 1708 in FIG. 20), and initiallyanchored or held in place using an expandable stent-like structure 1706.As discussed above, stent-like structure 1706 can be any suitable stentdevice or other anchoring device currently known or later developed. Inthis particular embodiment, however, stent-like structure 1706 isbio-absorbable, and thus, will dissolve within a given time period(e.g., about 6-8 months).

In accordance with this particular embodiment, and as illustrated inFIG. 20, sensor device 1700 is connected to anchoring device 1706, sothat sensor device 1700, and in particular, the one or more fins 1704,are positioned near the wall of vessel 1708. The device 1700 may beconnected to the anchoring device 1706 by a tether, a mold, dissolvablesutures, and the like. In any event, by placing the fins or extensions1704 near the vessel wall, tissue from the vessel will fibrose or growover the fins 1704, securing the sensor device 1700 in the vessel. Asone skilled in the art will appreciate, it may take time for fibroustissue to form over extensions 1704. As such, a relatively slowdissolving bio-absorbable anchoring device 1706 is typically used toinitially secure sensor device 1700 in place. As one skilled in the artwill appreciate, the vessel tissue typically will fibrose overextensions 1704 within a period between about 3 months and 6 months,which is typically before anchor device 1706 will completely dissolve.

In one embodiment, sensor device 1700, including extensions 1704 areformed from a bio-compatible material, such as stainless steel,titanium, nitinol, or some other bio-compatible material. In someembodiments, sensor mechanism 1702 and extensions 1704 are formed of thesame material. In other embodiments, sensor mechanism 1702 andextensions can be formed of different materials. In yet otherembodiments, extensions 1704 can comprise dacron, nylon or otherbio-compatible graphs or patches, making it easier for tissue to adherethereto. As one skilled in the art will appreciate, any number ofextension 1704 can be used, and extensions 1704 can be any suitablesize, shape and/or material. Thus, embodiments of the present inventionare not limited to any particular material or extension 1704configuration illustrated and/or described herein. Further, in stillother embodiments, sensor device 1700 can be coated with one or moredrugs that might help reduce inflammation and/or encourage or facilitatetissue fibrosis. Such drugs are currently known in the art.

In some embodiments, a fabric, such as Gore-Tex® (gore), may be placedbetween the stent and the sensor or actuator. The placement of thisfabric facilitates in keeping the tissue from attaching to the sensoritself and only allows the tissue to grow around the stent. As such, thesensor, actuator, or some part of the circuitry such as the battery, maybe detached, removed or replaced during a surgical procedure at a latertime. For example, in FIG. 14 the sensor or actuator 1402 may beremoved, replaced, and reattached to anchoring mechanism 1402 with a newsensor or actuator. In some embodiments, gore may also be used to coverboth sides of the stent. In these embodiments, the stent is sandwichedbetween two layers of gore and the physical expansion of the stent holdsthe device in place, even with the gore sheets on either side. However,since tissue can not grow through the stent due to the gore, the entirestent may be more easily removed at a later time.

One embodiment, as illustrated in FIG. 20, has a sensor device 1700placed within the anchoring structure 1706. FIG. 21 shows an axial viewof this embodiment. However, the anchoring structure 1706 may be placedon one side of the sensor device 1700. Or, an anchoring structure may beattached to both sides of the sensor or actuator's extensions or fins1704. This type of dual attachment of the sensor device 1700 to one ormore anchoring structures 1706 may help facilitate more accurate finalpositioning of the sensor as both sides of the device may be anchored inplace before the tissue grows around the device.

FIG. 22 shows yet another embodiment of an IMD anchoring system 1800. Inthis particular embodiment, anchoring system 1800 comprises an anchoringdevice 1802, a sensor 1804, and one or more connection structures 1806for connecting sensor 1804 to anchoring device 1802. In this particularembodiment, connection structures 1806 are configured to secure sensor1804 so that the sensor will reside near the middle of a blood vessel.By placing the sensor 1804 near the middle of the vessel, the sensor1804 will reside in the predominant blood flow that occurs in the middleof the vessel, avoiding edge effects, such as slower blood flow, deadzones, and perhaps clotting issues.

In one embodiment, anchoring device 1802 can include a stent-likestructure, as discussed above. Further, connection structures 1806 cancomprise any structural configuration that will secure sensor 1804 in adesired location. For example, connection structures 1806 can compriseone or more strut-type structures configured to hold sensor 1804 infront of, or in back of anchoring device 1802. In this particularembodiment, the strut-type structures can be made of the same materialas the stent-like structure 1802, or other materials can be used.Further, instead of securing sensor 1804 in front of, or in back ofanchoring device 1802, connection structures can be used to securesensor 1804 within anchoring device 1802, but still near the middle ofthe vessel. In addition, as discussed above, sensor 1804 can beconfigured to communicate with implantable medical devices (IMDs), suchas cardiac rhythm management device, and/or devices outside of a patientbody.

FIGS. 23-25 show additional embodiments of anchoring systems 1900, 1910,and 1920. In these embodiments, anchoring structures 1902, 1912, and1922 can be used to secure sensors 1904, 1914, and 1924 within a bodilyvessel (such as a blood vessel) 1906, 1916, and 1926, respectively. Insome embodiments, the anchoring structure can be secured in place bysurgical placement, and in other embodiments, the anchoring structurecan be placed in a blood vessel, and then allowed to float or flow withthe blood stream until the anchoring structure lodges in a suitablelocation to place the sensor.

In some embodiments (e.g., the embodiments illustrated in FIGS. 23-25),the anchoring structure can comprise a vena cava (“IVC”) filter devicehaving a sensor attached to it. For example, as illustrated in FIG. 23,a sensor 1904 can be connected to the IVC filter using a rigid ornon-rigid tether connection. In other embodiments, such as theembodiments illustrated in FIGS. 24 and 25, sensors 1914 and 1924 can beincorporated into the structure of the IVC filter. In some embodiments,the sensor can be placed so that it is approximately near the center ofthe vessel to take advantage of the center flow of the vessel, and inother embodiments, the sensor can be configured so that it is securednear the wall of the vessel. Further, any suitable IVC filter device canbe used. Examples of suitable IVC filters include, but are not limitedto, an LGM filter, a Gunther tulipe filter, an Antheor filter, a DILfilter, a Keeper filter, a FCP2002 filter, a Mobin-Uddin filter, aKimray-Greenfield filter, a Simon nitinol filter, a titanium Greenfieldfilter, a Bird's Nest filter, or any other suitable IVC filter device.Further, in other embodiments, the anchoring structures may not be IVCfilters, but may comprise structures having legs or extensions forsecuring a sensor within a vessel. In these embodiments, the legs orextensions can be configured to lodge in the vessel in a manner similarto the IVC filters, thus securing the sensor in place.

In one embodiment, the anchoring structures are designed to be securedin the pulmonary artery, which branches and tapers as it flows towardthe lungs. In this particular embodiment, the anchoring structure can beplaced in the pulmonary artery, and then allowed to flow with bloodstream until the anchoring structure lodges in a desired location. Oncesecured, the sensor can collect the desired data measurements. As oneskilled in the art will appreciate, the size of the anchoring structurecan control the location in which it will lodge. Also, as one skilled inthe art will appreciate, the anchoring structure can be placed in otherblood vessels, as well. Thus, embodiments of the present invention arenot limited to use in the pulmonary artery.

A discussed above, sensors 1904, 1914 and 1924 can be configured tocommunicate with implantable medical devices (IMDs), such as cardiacrhythm management devices, and/or devices outside of a patient's body.

FIG. 26 shows a cross-sectional view of a heart 2600. As illustrated,heart 2600 includes an atrium septal wall (not shown) separating leftatrium 2612 from right atrium 2614, and a ventricular septal wall 2620separating left ventricle 2622 from right ventricle 2624.

In accordance with another embodiment of the invention, a sensoranchoring device can be embedded in a separating or enclosing wall ofthe heart, for example, atrium septal wall or ventricular septal wall2620. In FIGS. 27A-27E, one method of inserting a sensor anchoringdevice in accordance with this embodiment is shown. In this particularembodiment, a sensor 2708 can be embedded inside or attached to aplug-like anchoring structure, which then can be placed in any cardiacseparating or enclosing wall 2704 (e.g., the septal wall). In accordancewith this particular embodiment; a physician may be able to perform twofunctions at once: (1) fill a preexisting hole or slit in a cardiacseparating wall in order to prevent blood from crossing from one side toanother; and (2) use the plug as an enclosure for the placement of aphysiologic parameter sensor. In other embodiments, a physician maycreate a hole or slit to place a sensor, and the plug-like anchoringstructure can be used to place the sensor and plug and/or seal the slitor hole.

FIGS. 27A-27E illustrate one embodiment of a method for anchoring asensor in a cardiac separating wall, such as the septal wall. FIG. 27Aillustrates a cardiac separating wall (e.g., septal wall) 2704 with ahole or slit 2702 for placing an anchoring structure with sensor. Asillustrated in FIG. 27B a physiologic parameter sensor 2708 embedded inor attached to a plug-like anchoring structure 2710 can be inserted intoa pre-anchoring slit 2702 (either a nature hole or a surgically createdhole or slit) using, for example, a guide catheter 2706. In thisembodiment, the guide catheter has the anchor/sensor assembly embeddedin it. To place the plug-like anchor 2710 (with sensor 2708) in thedesired location, the guide catheter 2706 is placed in the hole or slit2702 (FIG. 27B). Then, the guide catheter 2710 is retracted, causingplug ends 2712 and 2714 of the anchor device 2710 to expand (FIGS. 27Cand 27D). The plug ends 2712 and 2714 form a seal so that blood cannotflow through hole 2702 or around anchor structure 2710. FIG. 27E showsan end view of plug end 2712 of the anchoring device 2710. In oneembodiment, the anchoring device can be a septal plug currently known inthe art. In this embodiment, however, the septal plug is equipped with asensor, as discussed.

FIG. 28 is a flow diagram 2800 illustrating delivering, positioning, andanchoring a plug-like structure into a pre-anchoring slit according toone embodiment of the present invention. At block 2810, a pre-anchoringslit is located, or surgically created if one does not exist, in thecardiac wall. An IMD is attached to a plug-like anchoring structure atstep 2820. Then, the plug-like anchoring structure is inserted into thepre-anchoring slit at step 2830. At step 2840, using a guide catheter,the plug-like anchoring structure is positioned and then repositioned,at step 2850, as necessary. Once the final placement of the plug-likeanchoring structure has been achieved, the guide catheter is retracted,resulting in the expansion of the plug ends at step 2860.

FIG. 29 is a flow diagram illustrating an exemplary algorithm 2900 forcontrollably positioning and anchoring an IMD at a location in a bodilyvessel. At block 2910, a deflated balloon is inserted through acollapsed stent and an IMD is attached to the stent using, for example,one of the attachment methods described above. The stent with balloonand IMD are then inserted into a catheter.

At block 2920, the catheter is advanced into the bodily vessel to afirst location. The first location is typically selected to be close tothe desired location. At block 2930, the balloon is partially inflated,thereby partially expanding the stent. By partially inflating theballoon, the positioning can be controlled by enabling laterrepositioning, if desired. With the balloon partially inflated, one ormore physiologic parameter measurements are obtained from the IMD (e.g.,blood pressure, temperature, strain, motion, etc.) at block 2950. Themeasurements are tested for validity. Testing the measurements caninvolve determining whether numerical values are detected and that thevalues are reasonable.

At decision block 2960, it is determined whether the measurements arevalid. If the measurements are not valid, block 2940 repositions thestent to another location by moving the catheter. After the stent isrepositioned to the other location, block 2950 again obtains and testsmeasurements from the IMD. Repositioning can continue until block 2960determines that the measurements are valid. If the measurements arevalid, the balloon is fully inflated at block 2970 at the currentlocation. By fully inflating the balloon, the stent if fully expanded.The fully expanded stent frictionally engages with walls of the bodilyvessel to secure the stent within the bodily vessel.

As discussed, FIG. 29 illustrates a process for positioning a sensorusing a balloon-deployable stent. A different embodiment could includeself-expending stent that carries the sensor. In this embodiment, theself-expanding stent can be partially deployed and tested prior to fulldeployment. If test measurements taken after partial deployment are notinformative, invalid, or for any other reason, considered undesirable,or for any other reason (e.g., patient discomfort), the self-expandingstent can be moved to another location, tested, and so on. When validtest measurements are obtained at a location, the stent can be fullyexpanded at that location.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. Many other embodiments will be apparent to those of skill inthe art upon reviewing the above description. The scope of the inventionshould, therefore, be determined with reference to the appended claims,along with the full scope of equivalents to which such claims areentitled. In the appended claims, the terms “including” and “comprising”are open-ended, that is, a system, device, article, or process thatincludes elements in addition to those listed after such a term in aclaim are still deemed to fall within the scope of that claim.

1. A system for processing signals sensed by an implantable PAP sensor,the system comprising: a wireless communication circuit adapted toreceive a pulmonary artery pressure (PAP) signal from the implantablePAP sensor; and a PAP signal processor coupled to the wirelesscommunication circuit, the PAP signal processor including a signalisolation module adapted to isolate a plurality of signals from the PAPsignal.
 2. The system of claim 1, wherein the signal isolation modulecomprises at least one of a cardiac signal isolation module adapted toisolate one or more cardiac signals from the PAP signal and arespiratory signal isolation module adapted to isolate one or morerespiratory signals from the PAP signal.
 3. The system of claim 1,wherein the PAP signal processor further comprises an atmosphericpressure adjustment module adapted to adjust the PAP signal using anatmospheric pressure, and further comprising a barometer,communicatively coupled to the atmospheric pressure adjustment module,to sense the atmospheric pressure.
 4. The system of claim 1, wherein thePAP signal processor further comprises a posture adjustment moduleadapted to adjust the PAP signal using a posture signal, and furthercomprising a posture sensor, communicatively coupled to the postureadjustment module, to sense the posture signal.
 5. The system of claim1, wherein the PAP signal processor further comprises a pruning moduleto algorithmically prune specified type outlier components from the PAPsignal.
 6. The system of claim 1, wherein the cardiac signal isolationmodule comprises an adaptive filter having a pass-band dynamicallyadjusted using a physiological signal or parameter.
 7. The system ofclaim 1, wherein the respiratory signal isolation module comprises anadaptive filter having a pass-band dynamically adjusted using aphysiological signal or parameter.
 8. The system of claim 1, wherein thecardiac signal isolation module comprises a first adaptive filter havinga first pass-band dynamically adjusted using a heart rate, and therespiratory signal isolation module comprises a second adaptive filterhaving a second pass-band dynamically adjusted using the heart rate, andfurther comprising a heart rate detector to detect the heart rate. 9.The system of claim 1, wherein the cardiac signal isolation modulecomprises a triggered sampler to sample the PAP signal at apredetermined type event in each cycle of a cyclic physiological signal.10. The system of claim 9, wherein the cyclic physiological signal is arespiratory signal indicative of a predetermined type event in eachrespiratory cycle, and further comprising a respiratory sensor, coupledto the PAP signal processor, to sense the respiratory signal.
 11. Thesystem of claim 1, wherein the signal isolation module comprises one ormore of: an atmospheric pressure signal isolation module to isolate anatmospheric pressure signal from the PAP signal; a posture signalisolation module to isolate a posture signal from the PAP signal; aweather signal isolation module to isolate a weather signal from the PAPsignal; an altitude signal isolation module to isolate an altitudesignal from the PAP signal; a Valsalva signal isolation module toisolate a Valsalva signal from the PAP signal; and a Mueller signalisolation module to isolate a Mueller signal from the PAP signal.
 12. Asystem for use in a body having a pulmonary artery, the systemcomprising: an implantable pulmonary artery pressure (PAP) sensorconfigured for placement in the pulmonary artery to sense a PAP signal;and an implantable medical device communicatively coupled to theimplantable PAP sensor, the implantable medical device including a PAPsignal processor including a signal isolation module adapted to isolatea plurality of signals from the PAP signal.
 13. The system of claim 12,wherein the signal isolation module comprises at least one of a cardiacsignal isolation module adapted to isolate one or more cardiac signalsfrom the PAP signal and a respiratory signal isolation module adapted toisolate one or more respiratory signals from the PAP signal.
 14. Thesystem of claim 12, wherein the implantable medical device iselectrically connected to the implantable PAP sensor.
 15. The system ofclaim 12, wherein the implantable medical device is communicativelycoupled to the implantable PAP sensor using an ultrasonic telemetrylink.
 16. The system of claim 12, wherein the implantable medical deviceis communicatively coupled to the implantable PAP sensor via a far-fieldradio frequency telemetry link.
 17. The system of claim 12, wherein theimplantable medical device is communicatively coupled to the implantablePAP sensor via an inductive telemetry link.
 18. The system of claim 12,wherein the implantable medical device further comprises a therapydelivery device to deliver one or more therapies.
 19. The system ofclaim 18, wherein the implantable medical device further comprises acontroller coupled to the therapy circuit, the controller adapted tocontrol the delivery of the one or more therapies using at least one ofthe isolated signals.
 20. The system of claim 19, wherein the therapydelivery device includes a pacing output circuit, and the controller isadapted to control a delivery of a cardiac resynchronization therapyfrom the pacing output circuit.
 21. The system of claim 12, wherein thePAP signal processor further comprises an atmospheric pressureadjustment module adapted to adjust the PAP signal using an atmosphericpressure, and further comprising an external pressure calibratorcommunicatively coupled to the implantable medical device, the externalpressure calibrator including a barometer to sense the atmosphericpressure.
 22. The system of claim 12, wherein the PAP signal processorfurther comprises a posture adjustment module adapted to adjust the PAPsignal using a posture signal, and further comprising a posture sensor,communicatively coupled to the posture adjustment module, to sense theposture signal.
 23. The system of claim 12, wherein the signal isolationmodule comprises one or more of: an atmospheric pressure signalisolation module to isolate an atmospheric pressure signal from the PAPsignal; a posture signal isolation module to isolate a posture signalfrom the PAP signal; a weather signal isolation module to isolate aweather signal from the PAP signal; an altitude signal isolation moduleto isolate an altitude signal from the PAP signal; a Valsalva signalisolation module to isolate a Valsalva signal from the PAP signal; and aMueller signal isolation module to isolate a Mueller signal from the PAPsignal.
 24. A method, comprising: receiving a pulmonary artery pressure(PAP) signal from an implantable PAP sensor through a wirelesscommunication link; and isolating a plurality of signals from the PAPsignal.
 25. The method of claim 24, wherein the plurality of signalscomprises one or more cardiac signals and one or more respiratorysignals.
 26. The method of claim 24, wherein receiving the PAP signalcomprises receiving an ultrasonic signal through an ultrasonic telemetrylink and demodulating the ultrasonic signal.
 27. The method of claim 24,wherein receiving the PAP signal comprises receiving an electromagneticsignal through a far-field radio-frequency telemetry link anddemodulating the electromagnetic signal.
 28. The method of claim 24,wherein receiving the PAP signal comprises receiving a magnetic signalthrough an inductive telemetry link and demodulating the magneticsignal.
 29. The method of claim 24, further comprising adjusting the PAPsignal using an atmospheric pressure before isolating the plurality ofsignals.
 30. The method of claim 29, further comprising adjusting thePAP signal using a signal indicative of posture before isolating theplurality of signals.
 31. The method of claim 24, wherein isolating theplurality of signals comprises: filtering the PAP signal using at leastone adaptive filter having a pass-band; and dynamically adjusting thepass-band using a physiological signal or parameter.
 32. The method ofclaim 31, wherein dynamically adjusting the pass-band comprises:detecting a heart rate; and adjusting the pass-band dynamically as afunction of the heart rate.
 33. The method of claim 24, whereinisolating the plurality of signals comprises isolating the one or morecardiac signal by sampling the PAP signal at a predetermined type eventin each cycle of a cyclic physiological signal.
 34. The method of claim24, wherein the plurality of signals comprises one or more of anatmospheric pressure signal, a posture signal, a weather signal, analtitude signal, a Valsalva signal, and a Mueller signal.
 35. The methodof claim 24, further comprising delivering one or more therapies usingan implantable medical device.
 36. The method of claim 35, furthercomprising controlling the delivery of the one or more therapies usingone or more signals selected from the plurality of signals isolated fromthe PAP signal.
 37. The method of claim 36, wherein the one or moretherapies comprises a cardiac resynchronization therapy.